The state-of-the-art in antilock brake systems involves the integration of the electronic control assembly with the brake system's solenoid valve assemblies and hydraulic control unit. Some prior designs have solenoid valve assemblies press-fit onto valve stems in a separate hydraulic control unit. This assembly is, in turn, connected to an electronic controller via a wiring harness.
For an integral assembly, the solenoid assemblies must be assembled into the electronic assembly before being mated to hydraulic valve stems in order to form a magnetic interconnect. Because of this integration, it is no longer feasible to press-fit an assembly of solenoid assemblies onto the valve stems. Some adjustability or tolerance, which allows for motion of the individual solenoid assemblies relative to their respective valve stems, is needed so that tolerances between the locations of the valve stems can be accounted for. Also, a bias or force must be exerted by each solenoid assembly toward its respective valve to both insure a continuous magnetic path and to prevent rattling when the solenoid assemblies are actuated and when they are subjected to vehicle vibrations. Further, with an integrated system, there needs to be a seal between each of the solenoid assemblies and the electronic assembly to prevent moisture and other contaminants from entering the assembly.
Current integrated antilock brake systems typically account for tolerances and sealing of the electronics when forming the integrated assembly by having the solenoid assemblies secured using a potting compound. Typically, the solenoid assemblies are mechanically fixtured for alignment and then set into position and soldered directly to the circuit board of the electronics control unit, and an elastomeric potting compound is dispensed or injected around them and cured to secure them in place and seal the electronic assembly.
Using potting compound to align and secure the solenoid assemblies is not a preferred type of manufacturing process since the integrated assembly formed is both non-repairable and the cure oven process may emit regulated pollutants. Further, potting the solenoid assemblies requires special manufacturing fixturing and cure ovens. The potting compound also adds a considerable amount of weight to an assembly, which is undesirable.
The need exists, then, for easier manufacturing and assembly, producing a lighter weight integrated assembly, with lower environmental impact, while meeting all of the requirements of a repairable solenoid coil assembly for an integrated antilock braking system.